by Kurt Prange

Passive (i.e. battery-free) electric guitar circuits are relatively simple and the possibilities for customization are endless. A basic understanding of pickups, potentiometers, capacitors and switches is all you need to get creative and take more control of your instrument’s voice on an electronic level.

Where does the electric guitar signal come from?

Pickups are transducers that convert the mechanical energy of a vibrating guitar string into electrical energy by way of electromagnetic induction. It is a fundamental concept studied in physics and electronics that a changing magnetic field will generate a current through a coil of wire. The electric guitar pickup uses permanent magnets and pole pieces to form a steady magnetic field in the vicinity of each individual guitar string.

An opposite magnetic polarity is induced in the metallic (steel core) guitar string when mounted above its respective pole piece and when the string moves, the otherwise steady magnetic field changes accordingly. Wire is wrapped around the poles thousands of times to form a coil within the magnetic field to pick up an induced current and voltage.

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In every key there are seven chords than can be numbered from 1 to 7 using Roman Numerals. In this example we’ll take the key of G. So here are the chords(the chord fingerings are pictured above):

I …… II …… III …… IV …… V …… VI ……VII
G … Am …. Bm ….. C …… D …… Em …. F#dim



The I, IV, V chords are always major chords. The II, III, IV are always minor chords. The VI chord is not used that often in popular music, so I’ll leave it alone for now.

What can you do with this knowledge?

Create songs, baby! When you play a I – VI – IV – V progression in the key of G, you know that you’re playing G – Em – C – D. If you play around with different combinations of chord progressions, you’ll start to notice the familiar sounds associated with song structure.

Here are some other popular progression to try:

So go through each key and figure out the chord progressions, learn the chords and start working out combinations to work on your own song. Don’t over complicate it, just do it an listen as you play. If you need help with your chord fingerings, use the widget in the right hand column.

The 3rd issue of Interactive Guitar Magazine is out and it includes an interview with Zakk Wylde, plus in depth looks at some of his kit: Zakk’s Gibson Les Paul, the Marshall JCM800 amp and the MXR Zakk Wylde pedals.

Other interviews continue the heavy metal theme with Stuart Bull quizzing Def Leppard’s guitar ace, Phil Collen, Jamie Humphries meeting Whitesnake’s Doug Aldrich and Gary Cooper profiling that master of chords Pete Townsend. All the interviews are supplemented with videos showing you how play songs by these great guitarists and the techniques they use.

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